Unitarity relation for deep inelastic scattering

Saturating the multiparticle states in the unitarity relation for virtual Compton scattering by two-particle states consisting of an infinite set of high mass vector mesons and a nucleon leads to a non-linear integral equation the solution of which determines the behaviour in the scaling limit and the non-forward scaling functions for deep inelastic scattering.     

Low-energy theorem for virtual compton scattering and generalized sum rules of the nucleon

We formulate the low-energy theorem for virtual Compton scattering off a nucleon and examine its consequences for generalized nucleon polarizabilites. As a result of a new, model-independent definition of the low-energy limit for doubly virtual Compton scattering, all generalized sum rules of the nucleon have a continuous limit for real photons and obtain contributions from the t channel that were not included previously.     

Nucleon polarizabilities in real and virtual Compton scattering: Recent theoretical issues

We review recent developments in the theoretical investigation of the nucleon polarizabilities. We first report on the static polarizabilities as measured in real Compton scattering, comparing and interpreting the results from various theoretical approaches. In a second step, we extend the discussion to the generalized polarizabilities which can be accessed in virtual Compton scattering, showing how the information encoded in these quantities can provide a spatial interpretation of the induced polarization densities in the nucleon.     

Virtual Compton scattering off the pseudoscalar meson octet

We present a calculation of the virtual Compton scattering amplitude for the pseudoscalar meson octet in the framework of chiral perturbation theory at O(p ⁴). We calculate the electromagnetic generalized polarizabilities and compare the results in the real Compton scattering limit to available experimental values. Finally, we give predctions for the differential cross section of electron-meson bremsstrahlung.     

Time-reversal invariance-like relations for spin-effects in elastic and inelastic reactions; vector-meson photoproduction versus compton scattering from nucleons

For elastic scattering, relations between spin-effects (for example, the well-known asymmetry-polarization equality) follow from time-reversal invariance. We show that if certain amplitude combinations vanish, there are strikingly similar relations between spin-effects for elastic and also inelastic reactions. This vanishing of amplitude combinations (denoted M-purity) corresponds asymptotically to purely natural or purely unnatural parity in the crossed channel. The M-purity relations hold for spin-configurations much more general than do the corresponding time-reversal invariance relations.The experimental evidence for purely natural parity exchanges in high energy vector meson photoproduction from nucleons is shown to be good for all amplitudes involving nonzero meson helicity, but less conclusive for the zero helicity ones. Using time-reversal invariance and a vector meson-dominance argument, this implies no unnatural parity contributions in high energy Compton scattering from nucleons.Because of this empirical evidence for M-purity in these two processes, a detailed application to spin-effects in Compton scattering and in vector meson photoproduction is made. Some time-reversal invariance relations in Compton scattering resemble the corresponding M-purity relations though the applicability of the two is different, and there are examples where only one of the two exists. Out of our illustrations, the only M-purity relations which change in form due to the extra amplitudes present in the inelastic reaction are the M-purity analogue and extensions of the asymmetry-polarization equality (of Compton scattering) referring to the photon; the change is the appearance of the elements ?⁰⁰ of the vector meson density-matrix ?. Our other examples of M-purity relations do not change in form in going over from the elastic reaction (Compton scattering) to the inelastic reaction (vector meson photoproduction).     

Polarized electron scattering on spin zero and polarized spin-1/2 targets: Deep inelastic scattering,elastic electron-muon scattering,and elastic electron-nucleon scattering

A covariant formulation is developed and used to derive cross sections for the analysis of experiments in which polarized electrons (muons) are scattered from spin-zero and from polarized spin-1/2 targets. The analysis is based upon the single virtual photon representation of the electromagnetic interaction, initially, neither high-energy nor low-energy approximations are made so that one may derive results in which the orientation of the polarization vectors of the interacting particles changes as a result of the scattering. The general formulation is valid for all polarization configurations for the electron and nucleon in deep inelastic scattering, and for all polarization configurations for the initial and final state particles in elastic scattering. From the general covariant results, specific cross sections are derived for deep inelastic scattering as well as elastic scattering of electrons on muons, nucleons, and spin zero targets. In the latter case, the actual polarization vector for the scattered electron is determined. In the other cases discussed, this vector may be obtained from the cross sections. In addition, a method is presented for defining covariant cross sections, and this method is used to obtain results in the center-of-mass system as well as the laboratory system. Furthermore, explicit cross sections for virtual photon absorption are derived. Finally, in the appendices, an alternative method for the evaluation of traces is given as well as a discussion of the relativistic limit.     

Measurement of soil water using Compton scattering

Compton scattering method has been used as a possible tool in the study of the properties of soil for agricultural purposes. In this study, the soil water is determined by using Compton scattering method. The soil sample was collected from Erzurum and a 2 × 2 in. NaI (Tl) scintillation detector measured Compton scattered radiation from the soil sample. The radioactive source used in the experiment was a ¹³³Ba. The soil samples were irrigated by adding known quantities of water and a standard curve was constructed with the amount of water added versus Compton scattering intensity. It was observed that Compton scattering method in measurement of the soil water has advantages such as practical, inexpensive, non‐destructive and fast analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Demonstration of spectrally resolved x-ray scattering in dense plasmas

We present the first spectrally resolved x-ray scattering measurements from solid-density plasmas. The scattering spectra show the broadened Compton down-shifted feature allowing us to determine the electron temperature and density with high accuracy. In the low temperature limit, our data indicate that the ionization balance reflects the electrons in the conduction band consistent with calculations that include quantum mechanical corrections to the interaction potential.     

康普顿散射中反冲电子方向的正确画法

指出了某些教材中康普顿散射示意图画法的不妥之处,并严格推导了康普顿散射中反冲电子的散射角,给出了正确的康普顿散射示意图.     

Compton scattering study of orthorhombic sulphur

The Compton profiles of orthorhombic sulphur crystals have been measured the scattering vector perpendicular to the crystal planes (110) and (001) using 60 keV radiation from a ²⁴¹Am source. Significant anisotropy was observed in the electron momentum distribution. Fourier transformed Compton profiles were compared with theoretical autocorrelation functions for a S₈ ring molecule. It is shown that the observed anisotropy can be only partially interpreted in terms of intermolecular interactions. The strong correlation, observed in the direction perpendicular to the plane of the S₈ ring indicates a meaningful ring — ring interaction in the orthorhombic sulphur crystal.     

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应用多光子非线性Compton散射模型,研究了Compton散射对等离子体中激光衰减特性的影响.提出了Compton散射是影响激光衰减的一个重要机制,给出了激光能量和功率衰减值的表达式,并进行了数值模拟.结果表明,Compton散射对等离子体中传输的激光能量和功率衰减值有较大影响,理论计算和数值模拟符合得很好.这也为判断等离子体中发生Compton散射提供了依据.     

对非线性康普顿散射几种改进物理模型的比较

非线性康普顿散射被认为是未来超短超强激光与物质相互作用中的主导性物理过程之一。目前大多数相关研究都基于一种主流的非线性康普顿散射物理模型,该模型假设辐射形成距离足够短、对初态和末态自旋求平均与求和、并忽略了参与散射的激光光子的能动量。近年来,一些研究为了在更广阔的参数空间内,更准确地描述非线性康普顿散射,也对这个主流物理模型提出了几种修正和改进。回顾了对非线性康普顿散射主流物理模型进行的几种改进和修正,介绍了它们的适用范围,分析了它们的基本性质并对其物理效应进行了简单讨论。     

Exchange effects in photon scattering off the deuteron

Detailed calculations of elastic photon-deuteron scattering cross sections for photon energies up to about the π-production threshold are presented. The scattering amplitude is decomposed into scalar, vector and tensor polarizabilities for the various electric and magnetic multipole combinations. This includes a general multipole expansion of the two-photon operator. The imaginary part of the polarizabilities is determined from the contribution to the total cross section using the optical theorem. The real part is then obtained from dispersion relations. Special emphasis is laid on the discussion of exchange effects for both the resonance and the two-photon amplitude. These affect strongly the resonance amplitude whereas for the two-photon amplitude we find only a small effect beyond the important low-energy limit. Another important result is the large vector polarizability at higher energies related to the optical activity of the deuteron.     

Laser Compton scattering for a linearly polarized laser

Laser Compton light sources are potential candidates for the next generation of high-brightness X or γ-ray sources. When increasing the laser power to obtain intense X-ray laser, nonlinear Compton scattering happens. Nonlinear Compton scattering of linearly polarized laser beam is discussed in this paper. A complete transition probability formula is introduced and the polarization properties of final photons are discussed for different conditions.     

Low-intensity nonlinear spectral effects in compton scattering

Nonlinear effects are known to occur in Compton scattering light sources, when the laser normalized potential A approaches unity. In this Letter, it is shown that nonlinear spectral features can appear at arbitrarily low values of A, if the fractional bandwidth of the laser pulse Δ??1 is sufficiently small to satisfy A2Δ??1. A three-dimensional analysis, based on a local plane wave, slow-varying envelope approximation, enables the study of these effects for realistic interactions between an electron beam and a laser pulse, and their influence on high-precision Compton scattering light sources.     

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应用光声理论、相对论量子理论和电子与多光子集团非线性Compton散射模型,研究了Compton散射对掺杂固体中光声信号强度的影响。结果表明,当掺杂固体中发生电子与多光子集团之间的多光子非线性Compton散射时,在忽略光声转换效率的变化和基质晶格对介电函数贡献的情况下,耦合激光能量和磁感应强度是影响光声信号强度的两个主要因素,其中耦合磁感应强度起主导作用。Compton散射使光声信号强度随耦合光的磁感应强度和能量的增大而迅速增大。能量与光声信号声压之间存在对数线性关系,但它相对于Compton散射前的曲线下移。     

Compton散射对固体中激光能量与光声信号强度关系的影响

应用光声理论、相对论量子理论和电子与多光子集团非线性Compton散射模型,研究了Compton散射对掺杂固体中光声信号强度的影响。结果表明,当掺杂固体中发生电子与多光子集团之间的多光子非线性Compton散射时,在忽略光声转换效率的变化和基质晶格对介电函数贡献的情况下,耦合激光能量和磁感应强度是影响光声信号强度的两个主要因素,其中耦合磁感应强度起主导作用。Compton散射使光声信号强度随耦合光的磁感应强度和能量的增大而迅速增大。能量与光声信号声压之间存在对数线性关系,但它相对于Compton散射前的曲线下移。     

Temperature-dependent orbital degree of freedom of a bilayer manganite by magnetic compton scattering

We have measured temperature-dependent magnetic Compton profiles (MCPs) from a single crystal of La1.2Sr1.8Mn2O7. The MCPs, which involved the scattering of circularly polarized x rays, are in general related to the momentum density of all the unpaired spins in the system. Nevertheless, we show that when the x-ray scattering vector lies along the [110] direction, the number of magnetic electrons of a specific symmetry, i.e., d electrons of x(2)-y(2) symmetry, yield a distinct signature in the MCP, allowing us to monitor substantial changes in the occupancy of the dx(2)(-y(2)) states over the investigated temperature range of 5-200 K. This study indicates that magnetic Compton scattering can provide a powerful window on the properties of specific magnetic electrons in complex materials.     

Angular distributions of scattering intensities with the SAP code

Compton and Rayleigh scattering peak intensities and their ratio are used in reflection and transmission experiments to obtain information about the density of the investigated specimen. The ratio is preferred because it allows the reduction of the errors due to attenuation and geometry. In all cases it is fundamental to predict their angular distributions in order to design the optimal experiment for a given material. The code SAP (Scattering Angular distribution Plot) is a graphical tool to compute and plot Rayleigh and Compton differential cross‐sections (atomic and electronic), form factors and incoherent scattering functions. In this work, the code is improved by adding the computation of Rayleigh and Compton first‐order peak fluxes and intensities, and the Rayleigh‐to‐Compton peak ratio, in both, reflection and transmission geometries, for single elements, compounds and mixture of compounds, for monochromatic excitation in the range of 1–1000 keV. The new characteristics of the code are illustrated with some examples. Copyright © 2011 John Wiley & Sons, Ltd.